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October 31, 2012 -- Older women with early-stage, low-risk breast cancer who were treated with radiation therapy after breast-conserving surgery showed higher survival rates than those who did not have radiation therapy, a California study found. Results were presented at the American Society for Radiation Oncology (ASTRO) meeting.

Despite the positive finding, the study also showed a 6% decrease in the use of radiation after 2004 in this patient population. This might indicate that clinical guidelines on the use of radiation therapy in older women need to be revised, according to the researchers.

The study evaluated patient records of 27,559 women with early-stage breast cancer from the Surveillance, Epidemiology, and End Results (SEER) database from 2000 to 2008. The women were older than age 70, had tumors 5 cm or smaller, and were estrogen-receptor positive and node negative. One-third of the women were older than 80. All had undergone breast conservation surgery prior to radiotherapy and had at least one follow-up three months after completing treatment.

The study separated patients into two groups: those who had breast conservation surgery only and those who also received radiotherapy, according to lead author Dr. Mariam Korah from the University of Southern California Keck School of Medicine.

From 2000 to 2004, 72% of patients received radiation therapy, which decreased to 66% from 2005 to 2008. Patients were statistically more likely to undergo radiation therapy if they were younger than 80, received a diagnosis from 2000 to 2004, or if re-excision of the biopsy site was required for residual disease.

Patients who received radiation had a higher overall survival rate than those who did not, at 87% and 73% at the five- and eight-year follow-up points, respectively, compared with 69% and 49% for those who did not have radiotherapy. Radiation was also shown to slightly improve cause-specific survival rates. For patients who received radiation, the rates were 97% and 95% at the five- and eight-year follow-ups, compared with 95% and 91% for those who did not receive radiation.

A total of 4,573 deaths were recorded; 17% were attributed to breast cancer.

"The findings of this study suggest that current treatment guidelines, which allow for omission of radiation therapy for older women with early-stage, localized breast cancer, may need to be re-examined," Korah concluded.